Bicycles have been utilized as a means of transportation for over a hundred years and continue to grow in popularity. The mountain bike is one type of bike that has become more and more popular in recent years. These types of bikes are often used in rough terrain.
Operational or control cables typically extend from control levers, often secured to the bicycle handlebars, used to control both front and back wheel braking capacities and front and back shifting mechanisms such as the front and rear derailleurs. The operational or control cables are normally mounted along the outside of the tubular frame members, with various attachment members, such as clips. The cables can interfere with either the rider or other components of the bicycle, such as tool compartments, which are also attached to the frame exterior. In the case of mountain bikes, externally located cables are susceptible to damage from the surrounding environment, such as tree branches. Further, the cables also detract from the aesthetic appearance of the frame, as they may cover art or graphic logos on the bike frame.
To eliminate the appearance of cables on the exterior of bicycle frames, prior art attempts have been made to extend the cables through the interiors of tubular frame components. An early example is described in French Patent No. 982,877, which shows a bicycle frame in which the top tube consists of a hollow, tubular member having a forward cable outlet at a location near the head tube socket which is attached to the top tube, and a rearward cable outlet adjacent to the seat mast of the bicycle frame. A later example is described in German Patent Application No. 19712326, where at least one section of the base frame has an extruded profile tube section with at least one channel to accept a cable.
While the internal cable system of this type of frame eliminates the appearance of the cable on the exterior of the frame components, the forming of several openings along the top tube of a bicycle frame tends to weaken the wall of that tube, which would require either that the tube be made of a strong but heavy material such as steel, or that the tube walls be thickened if made of a relatively light material which would also add to the overall weight of the frame.
A more recent example of an internal cable routing system can be found in U.S. Pat. No. 5,478,100, where the cables are located inside of the top tube or down tube. However, the cables are still exposed from the brake or shift levers until they are routed into the frame some distance away.
In U.S. Pat. No. 4,768,798, the cables are routed directly into the frame at a point in front of the steering axis. In this case, the cables are also exposed until they reach the frame. In addition, the complexity of the steering tube is increased so that the cables can be routed through the tube and not interfere with the steering mechanism.
In recent years, it has also become recognized that the old-fashioned stationary handlebar and stem bicycle configuration can cause health problems such as lower back pain and wrist pain, due to the crouched body position necessary during bike riding. Many issued patents claim bicycle handlebars or stems that can be adjusted in one manner or another. U.S. Pat. Nos. 5,133,224, 5,273,302, 5,456,135, 5,727,427 and 5,737,967 describe various systems for adjusting bicycle handlebars or bicycle stems. However, these prior art adjustable handlebar stems would interfere with any internal cable routing system.
Accordingly, there is a need for an internal cable system for a bicycle frame that does not interfere with the steering mechanism and does not compromise the structural integrity of the tubes housing the cable, while permitting adjustable handlebars or stems.